The negative impact of the COVID-19 pandemic and changes in working conditions on workers’ behavior and mental health has been demonstrated using data from three complementary studies: 1 - The Coviprev survey (Santé publique France), conducted among the general population, examined changes throughout 2020 in a number of health indicators for employed individuals, including their mental health, sleep quality, and satisfaction with their current and future lives. The main finding is that 30.5% of employed workers reported symptoms of anxiety at the start of the lockdown, compared to 15.9% at the end of June 2020, and approximately one in five workers exhibited depressive symptoms at the start of both lockdown periods. Sleep disorders affected approximately two-thirds of employed workers and were more common among women than men. 2 - The survey on changes in working conditions and psychoactive substance use during the epidemic (Santé publique France and its partners), conducted among French employees, examined changes in alcohol and tobacco use during the first lockdown period between March and May 2020. The main finding is that 30% of respondents reported having increased their tobacco use, compared to 14% for alcohol. Among men, increased tobacco use during lockdown was associated with an increased workload (ORa = 2.5; p < 0.05), whereas for women, it was associated with a decrease in their usual workload (ORa = 2.7; p < 0.01). For alcohol, reporting a lighter workload than usual was associated with an increased risk of increased consumption, and this was true only for women (ORa = 2.2; p < 0.01). 3 - The Coset-Covid survey (Santé publique France) assessed the prevalence of anxiety and depressive disorders following the end of lockdown in June 2020 and examined the role of observed changes in work situations and organizational factors among self-employed workers and agricultural workers. The main finding is an increase in sleep difficulties, particularly among self-employed workers and employees in the agricultural sector, and a prevalence of anxiety (and depression) symptoms ranging from 7% to 22% (7% to 19%) in 2020.